This invention relates to rear projection apparatus, and more particularly to color image reproducing apparatus of the projection type in which images of different colors are projected onto a viewing screen in a superimposed manner to form the composite multicolor image seen by the viewer.
One known rear projection apparatus includes a rear transmitting screen and a projector for projecting an optical image onto a surface of the screen to view the image which appears on the opposite surface of the screen. The projector projects an image of a monochromic light or a plurality of images of monochromic or different color lights onto the screen to form a composite image on the screen. Particularly, in such color image reproducing apparatus, the projector includes a color television receiver and three small cathode-ray tubes having phosphor screens for individually forming red, green and blue component images. These component images are then optically projected onto the screen in a superimposed manner to form the desired multicolor image.
The quality of the image projected on the screen depends on the quality of the screen. Therefore, various screens have been developed. One well-known screen, which is called the "lenticular screen", includes a plurality of half column lenses arranged in parallel on a surface of a transparent plate.
Such lenticular screen, however, has low luminance at the circumference of the screen and color shift of the image according to the position of the viewer with respect to the screen as shown FIGS. 1 and 2.
In FIG. 1 image lights R, G and B are projected along the individual paths onto the convex surface SF of a screen S. These image lights pass through screen S and then emerge from the plane surface SB of screen S and pass along the different directions. This causes a difference in the color of the image between viewing the image as seen at the region K and viewing at the region L.
Further, when light is projected onto screen S, the intensity distribution of transmitted light is shown in FIG. 2. The light components in the projected direction do not have uniform intensity and the luminance on the plane surface of the screen. As a result, prior art devices employing lenticular screens have failed to reproduce good images.
Another type of known screen includes a plurality of half column lens arranged in parallel on both surface of a transparent plate as described in Japanese Patent Disclosure No. 100723/76. This type of screen may improve the luminance and color shift in either the horizontal or vertical direction of the screen, but may not improve the luminance and color shift in both directions. Therefore, such screen is not a satisfactory rear transmitting screen.